A technique is known in which a spout stopper (spout) having a screw portion is provided at a pour-out port of a container body for a product such as beverage, liquid seasoning, or cosmetic and the pour-out port is closed by a cap having a screw portion formed so as to be able to be brought into threaded engagement with the screw portion of the spout stopper. With the spout stopper and the cap, capping is enabled to be repeatedly performed, by bringing the screw portions into threaded engagement with each other even after the cap is removed for opening.
Patent Literature 1 discloses a cap body including a contact ring and an inner ring that are provided on the inner surface of the cap body at the sealing side and are brought into engagement with an end of a pour-out port body (spout stopper) at a pour-out port to enhance sealability.
Patent Literature 2 discloses a stopper including a spout having an end portion that is formed so as to spread at the same angle as the inclination angle of an inclined plate of a paper container, whereby when a content liquid is poured out, running-down of the liquid is less likely to occur and shutting-off of the liquid is good.
For mounting a spout stopper made of a resin material to a container body, an ultrasonic welding method is often used in which ultrasonic vibration is applied to a flange of the spout stopper to weld the flange.
Patent Literature 3 discloses a spout stopper (stopper with a pull ring) in which a cut-off portion (annular opening) is provided near the inner edge of a flange surface, whereby vibration occurring during ultrasonic welding is inhibited from being transmitted to a half-cut portion (annular thin brittle line) of a partition (blocking plate) that closes the spout stopper, thereby preventing occurrence of a crack.
Patent Literature 4 discloses a technique in which, in the above-described spout stopper having the cut-off portion, in order to inhibit projections, which are provided at equal intervals in the circumferential direction of a side wall for holding a container body between a flange and the projections, from being deformed by the energy of ultrasonic vibration, ribs are provided on the inner surface of the cut-off portion and at positions corresponding to the projections, whereby the energy of the ultrasonic vibration is dispersed and absorbed.